Effect of cigarette smoking on theophylline pharmacokinetics in rats

The effect of acute cigarette smoke inhalation on the plasma levels of theophylline administered orally and parenterally to rats has been studied. The animals were exposed to smoke containing low- or high-nicotine/tar concentration for 10 min immediately after oral, intraperitoneal (i.p.) or intravenous (i.v.) administration of theophylline. The plasma levels of theophylline when administered orally (20 mg kg-1) were lower in the two cigarette smoke-inhaling groups than in the non-smoking restrained control group, with the lowest values in the high-nicotine/tar group. The plasma levels (8 and 12 h after administration) in the high-nicotine/tar group when theophylline was administered i.p. (10 mg kg-1), were also slightly lower than in the non-smoking restrained control group but this was not significant. When theophylline was administered i.v. (5 mg kg-1), there was no difference between the high-nicotine/tar group and the non-smoking restrained control group. These data indicate that cigarette smoke inhalation causes suppression or delay of theophylline absorption from the gastrointestinal tract.